In general, when the sunroof of a vehicle is opened, droning noise, that is, noise and vibration due to interaction of the external air flowing over the opening (which is opened by the sunroof) of the sunroof on the roof of a vehicle and the internal air of the vehicle are generated. This phenomenon is caused by synchronization of an excitation frequency and an indoor sound field due to the flow of external air within a predetermined range of vehicle speed.
Further, when the sunroof is opened outward from a vehicle, the external air hits against the structure of the sunroof, thereby generating wind noise (noise due to a vortex produced by breakage of the streamline of air flowing around the sunroof while the vehicle is driven).
A wind deflector for optimizing airflow over the opening of sunroof is applied to the sunroof to reduce the droning noise and wind noise.
The wind deflector, which is a device that disturbs airflow over the roof of the vehicle to prevent booming droning noise when the sunroof is opened, is classified into a type that lifts airflow over the roof of the vehicle and a type that decreases the speed of airflow.
A mesh deflector is representative of the wind deflector that decreases the speed of airflow when passing through the mesh deflector, whereby the droning noise is suppressed.
The higher the mesh deflector, the more advantageous it is in reducing the droning noise by the sunroof, but the height is also a factor of causing the wind noise by the deflector. Accordingly, there is a limit in reducing droning noise and wind noise due to a sunroof (noise by external air hitting against the structure of a sunroof) by increasing the height of a deflector.